A fit to the simultaneous broadband spectrum of Cygnus X-1 using the transition disk model

Details A fit to the simultaneous broadband spectrum of Cygnus X-1 using the transition disk model A fit to the simultaneous broadband spectrum of Cygnus X-1 using the transition disk model

1997-12-23

arxiv.org/abs/astro-ph/9712309v1

Astrophys.J. 495 (1998) 407

Astronomy and Astrophysics

Astrophysics

8 figures. uses aasms4.sty, accepted by ApJ (Mar 98)

Scientific paper

10.1086/305278

We have used the transition disk model to fit the simultaneous broad band ($2-500$ keV) spectrum of Cygnus X-1 from OSSE and Ginga observations. In this model, the spectrum is produced by saturated Comptonization within the inner region of the accretion disk, where the temperature varies rapidly with radius. In an earlier attempt, we demonstrated the viability of this model by fitting the data from EXOSAT, XMPC balloon and OSSE observations, though these were not made simultaneously. Since the source is known to be variable, however, the results of this fit were not conclusive. In addition, since only once set of observations was used, the good agreement with the data could have been a chance occurrence. Here, we improve considerably upon our earlier analysis by considering four sets of simultaneous observations of Cygnus X-1, using an empirical model to obtain the disk temperature profile. The vertical structure is then obtained using this profile and we show that the analysis is self- consistent. We demonstrate conclusively that the transition disk spectrum is a better fit to the observations than that predicted by the soft photon Comptonization model. Since the temperature profile is obtained by fitting the data, the unknown viscosity mechanism need not be specified. The disk structure can then be used to infer the viscosity parameter $\alpha$, which appears to vary with radius and luminosity. This behavior can be understood if $\alpha$ depends intrinsically on the local parameters such as density, height and temperature. However, due to uncertainties in the radiative transfer, quantitative statements regarding the variation of $\alpha$ cannot yet be made.

Affiliated with

Also associated with

No associations

Rating

A fit to the simultaneous broadband spectrum of Cygnus X-1 using the transition disk model does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with A fit to the simultaneous broadband spectrum of Cygnus X-1 using the transition disk model, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A fit to the simultaneous broadband spectrum of Cygnus X-1 using the transition disk model will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-541317